Google Drive is a great service for both creating and storing spreadsheets if you don't want to shell out the cash for Excel. However, security is a concern, particularly when it comes to someone accessing your machine. This simple script from tech blog Skipser will allow you to encrypt all your data in a document and put it behind a password.

Initial setup is fairly straightforward. You'll be given a template spreadsheet that you can duplicate as needed (detailed instructions found at the source link). For each new document, run the script once to give it the permissions it needs at which point you can encrypt or decrypt your data at will.

You'll need to set up a password the first time you encrypt a spreadsheet, and enter it every time you want to access your data. Encryption is not automatic, so you'll want to make sure to lock up when you close the document. The first two lines are reserved for links in case you need to decrypt the spreadsheet from mobile, since the Drive app does not support scripts the way the webapp does. Check out the video above to see a demonstration of how to set this up.